Did the 2011 Tohoku Tsunami increase the risk of species invasions along the Gulf of Alaska?

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On March 11, 2011, a 9.0 magnitude earthquake struck 80 miles off the Pacific coast of Tohoku, Japan, triggering a tsunami. This tsunami washed over 5 million tons of debris away from Japan. 1.5 million tons of that marine debris remained afloat and was set adrift in the Pacific Ocean, much of it projected to make landfall along the west coast of North America. Marine debris, both natural and man-made, has a long history as a pathway for invasive species, which have the ability to inflict significant ecosystem harm. Such non-native and known invasive species have arrived along the west coast of North America attached to tsunami debris. Models predicted tsunami debris to make landfall along the Gulf of Alaska (GoA), and debris has been arriving since early 2012, bringing with it various species non-native to North America. This influx of non-native species has the potential to cause significant ecological and economic harm, making proper management and prevention critically important. This study aims to determine whether Alaska is at an increased risk of species invasion from the Japanese tsunami marine debris (JTMD) field by comparing debris in pre-tsunami (2010-2011) and post-tsunami years (2012-2014). Four categories of marine debris increased across the entire GoA, with the trend driven largely by debris in the eastern half of the GoA. These results—particularly the observed increases in foam and float debris in the eastern GoA—indicate that Alaska is at an increased risk of species invasion from the JTMD field. With a limited budget, management could increase the impact of preventative measures against invasive species from tsunami debris if focused along the eastern GoA.